[linux-block.git] / arch / s390 / kernel / kprobes.c

// SPDX-License-Identifier: GPL-2.0+
/*
 *  Kernel Probes (KProbes)
 *
 * Copyright IBM Corp. 2002, 2006
 *
 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
 */

#define pr_fmt(fmt) "kprobes: " fmt

#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/preempt.h>
#include <linux/stop_machine.h>
#include <linux/cpufeature.h>
#include <linux/kdebug.h>
#include <linux/uaccess.h>
#include <linux/extable.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/hardirq.h>
#include <linux/ftrace.h>
#include <linux/execmem.h>
#include <asm/text-patching.h>
#include <asm/set_memory.h>
#include <asm/sections.h>
#include <asm/dis.h>
#include "entry.h"

DEFINE_PER_CPU(struct kprobe *, current_kprobe);
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

struct kretprobe_blackpoint kretprobe_blacklist[] = { };

void *alloc_insn_page(void)
{
	void *page;

	page = execmem_alloc(EXECMEM_KPROBES, PAGE_SIZE);
	if (!page)
		return NULL;
	set_memory_rox((unsigned long)page, 1);
	return page;
}

static void copy_instruction(struct kprobe *p)
{
	kprobe_opcode_t insn[MAX_INSN_SIZE];
	s64 disp, new_disp;
	u64 addr, new_addr;
	unsigned int len;

	len = insn_length(*p->addr >> 8);
	memcpy(&insn, p->addr, len);
	p->opcode = insn[0];
	if (probe_is_insn_relative_long(&insn[0])) {
		/*
		 * For pc-relative instructions in RIL-b or RIL-c format patch
		 * the RI2 displacement field. The insn slot for the to be
		 * patched instruction is within the same 4GB area like the
		 * original instruction. Therefore the new displacement will
		 * always fit.
		 */
		disp = *(s32 *)&insn[1];
		addr = (u64)(unsigned long)p->addr;
		new_addr = (u64)(unsigned long)p->ainsn.insn;
		new_disp = ((addr + (disp * 2)) - new_addr) / 2;
		*(s32 *)&insn[1] = new_disp;
	}
	s390_kernel_write(p->ainsn.insn, &insn, len);
}
NOKPROBE_SYMBOL(copy_instruction);

/* Check if paddr is at an instruction boundary */
static bool can_probe(unsigned long paddr)
{
	unsigned long addr, offset = 0;
	kprobe_opcode_t insn;
	struct kprobe *kp;

	if (paddr & 0x01)
		return false;

	if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
		return false;

	/* Decode instructions */
	addr = paddr - offset;
	while (addr < paddr) {
		if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn)))
			return false;

		if (insn >> 8 == 0) {
			if (insn != BREAKPOINT_INSTRUCTION) {
				/*
				 * Note that QEMU inserts opcode 0x0000 to implement
				 * software breakpoints for guests. Since the size of
				 * the original instruction is unknown, stop following
				 * instructions and prevent setting a kprobe.
				 */
				return false;
			}
			/*
			 * Check if the instruction has been modified by another
			 * kprobe, in which case the original instruction is
			 * decoded.
			 */
			kp = get_kprobe((void *)addr);
			if (!kp) {
				/* not a kprobe */
				return false;
			}
			insn = kp->opcode;
		}
		addr += insn_length(insn >> 8);
	}
	return addr == paddr;
}

int arch_prepare_kprobe(struct kprobe *p)
{
	if (!can_probe((unsigned long)p->addr))
		return -EINVAL;
	/* Make sure the probe isn't going on a difficult instruction */
	if (probe_is_prohibited_opcode(p->addr))
		return -EINVAL;
	p->ainsn.insn = get_insn_slot();
	if (!p->ainsn.insn)
		return -ENOMEM;
	copy_instruction(p);
	return 0;
}
NOKPROBE_SYMBOL(arch_prepare_kprobe);

struct swap_insn_args {
	struct kprobe *p;
	unsigned int arm_kprobe : 1;
};

static int swap_instruction(void *data)
{
	struct swap_insn_args *args = data;
	struct kprobe *p = args->p;
	u16 opc;

	opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
	s390_kernel_write(p->addr, &opc, sizeof(opc));
	return 0;
}
NOKPROBE_SYMBOL(swap_instruction);

void arch_arm_kprobe(struct kprobe *p)
{
	struct swap_insn_args args = {.p = p, .arm_kprobe = 1};

	if (cpu_has_seq_insn()) {
		swap_instruction(&args);
		text_poke_sync();
	} else {
		stop_machine_cpuslocked(swap_instruction, &args, NULL);
	}
}
NOKPROBE_SYMBOL(arch_arm_kprobe);

void arch_disarm_kprobe(struct kprobe *p)
{
	struct swap_insn_args args = {.p = p, .arm_kprobe = 0};

	if (cpu_has_seq_insn()) {
		swap_instruction(&args);
		text_poke_sync();
	} else {
		stop_machine_cpuslocked(swap_instruction, &args, NULL);
	}
}
NOKPROBE_SYMBOL(arch_disarm_kprobe);

void arch_remove_kprobe(struct kprobe *p)
{
	if (!p->ainsn.insn)
		return;
	free_insn_slot(p->ainsn.insn, 0);
	p->ainsn.insn = NULL;
}
NOKPROBE_SYMBOL(arch_remove_kprobe);

static void enable_singlestep(struct kprobe_ctlblk *kcb,
			      struct pt_regs *regs,
			      unsigned long ip)
{
	union {
		struct ctlreg regs[3];
		struct {
			struct ctlreg control;
			struct ctlreg start;
			struct ctlreg end;
		};
	} per_kprobe;

	/* Set up the PER control registers %cr9-%cr11 */
	per_kprobe.control.val = PER_EVENT_IFETCH;
	per_kprobe.start.val = ip;
	per_kprobe.end.val = ip;

	/* Save control regs and psw mask */
	__local_ctl_store(9, 11, kcb->kprobe_saved_ctl);
	kcb->kprobe_saved_imask = regs->psw.mask &
		(PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);

	/* Set PER control regs, turns on single step for the given address */
	__local_ctl_load(9, 11, per_kprobe.regs);
	regs->psw.mask |= PSW_MASK_PER;
	regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
	regs->psw.addr = ip;
}
NOKPROBE_SYMBOL(enable_singlestep);

static void disable_singlestep(struct kprobe_ctlblk *kcb,
			       struct pt_regs *regs,
			       unsigned long ip)
{
	/* Restore control regs and psw mask, set new psw address */
	__local_ctl_load(9, 11, kcb->kprobe_saved_ctl);
	regs->psw.mask &= ~PSW_MASK_PER;
	regs->psw.mask |= kcb->kprobe_saved_imask;
	regs->psw.addr = ip;
}
NOKPROBE_SYMBOL(disable_singlestep);

/*
 * Activate a kprobe by storing its pointer to current_kprobe. The
 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
 * two kprobes can be active, see KPROBE_REENTER.
 */
static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
{
	kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
	kcb->prev_kprobe.status = kcb->kprobe_status;
	__this_cpu_write(current_kprobe, p);
}
NOKPROBE_SYMBOL(push_kprobe);

/*
 * Deactivate a kprobe by backing up to the previous state. If the
 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
 * for any other state prev_kprobe.kp will be NULL.
 */
static void pop_kprobe(struct kprobe_ctlblk *kcb)
{
	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
	kcb->kprobe_status = kcb->prev_kprobe.status;
	kcb->prev_kprobe.kp = NULL;
}
NOKPROBE_SYMBOL(pop_kprobe);

static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
{
	switch (kcb->kprobe_status) {
	case KPROBE_HIT_SSDONE:
	case KPROBE_HIT_ACTIVE:
		kprobes_inc_nmissed_count(p);
		break;
	case KPROBE_HIT_SS:
	case KPROBE_REENTER:
	default:
		/*
		 * A kprobe on the code path to single step an instruction
		 * is a BUG. The code path resides in the .kprobes.text
		 * section and is executed with interrupts disabled.
		 */
		pr_err("Failed to recover from reentered kprobes.\n");
		dump_kprobe(p);
		BUG();
	}
}
NOKPROBE_SYMBOL(kprobe_reenter_check);

static int kprobe_handler(struct pt_regs *regs)
{
	struct kprobe_ctlblk *kcb;
	struct kprobe *p;

	/*
	 * We want to disable preemption for the entire duration of kprobe
	 * processing. That includes the calls to the pre/post handlers
	 * and single stepping the kprobe instruction.
	 */
	preempt_disable();
	kcb = get_kprobe_ctlblk();
	p = get_kprobe((void *)(regs->psw.addr - 2));

	if (p) {
		if (kprobe_running()) {
			/*
			 * We have hit a kprobe while another is still
			 * active. This can happen in the pre and post
			 * handler. Single step the instruction of the
			 * new probe but do not call any handler function
			 * of this secondary kprobe.
			 * push_kprobe and pop_kprobe saves and restores
			 * the currently active kprobe.
			 */
			kprobe_reenter_check(kcb, p);
			push_kprobe(kcb, p);
			kcb->kprobe_status = KPROBE_REENTER;
		} else {
			/*
			 * If we have no pre-handler or it returned 0, we
			 * continue with single stepping. If we have a
			 * pre-handler and it returned non-zero, it prepped
			 * for changing execution path, so get out doing
			 * nothing more here.
			 */
			push_kprobe(kcb, p);
			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
			if (p->pre_handler && p->pre_handler(p, regs)) {
				pop_kprobe(kcb);
				preempt_enable_no_resched();
				return 1;
			}
			kcb->kprobe_status = KPROBE_HIT_SS;
		}
		enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
		return 1;
	} /* else:
	   * No kprobe at this address and no active kprobe. The trap has
	   * not been caused by a kprobe breakpoint. The race of breakpoint
	   * vs. kprobe remove does not exist because on s390 as we use
	   * stop_machine to arm/disarm the breakpoints.
	   */
	preempt_enable_no_resched();
	return 0;
}
NOKPROBE_SYMBOL(kprobe_handler);

/*
 * Called after single-stepping.  p->addr is the address of the
 * instruction whose first byte has been replaced by the "breakpoint"
 * instruction.  To avoid the SMP problems that can occur when we
 * temporarily put back the original opcode to single-step, we
 * single-stepped a copy of the instruction.  The address of this
 * copy is p->ainsn.insn.
 */
static void resume_execution(struct kprobe *p, struct pt_regs *regs)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	unsigned long ip = regs->psw.addr;
	int fixup = probe_get_fixup_type(p->ainsn.insn);

	if (fixup & FIXUP_PSW_NORMAL)
		ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;

	if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
		int ilen = insn_length(p->ainsn.insn[0] >> 8);
		if (ip - (unsigned long) p->ainsn.insn == ilen)
			ip = (unsigned long) p->addr + ilen;
	}

	if (fixup & FIXUP_RETURN_REGISTER) {
		int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
		regs->gprs[reg] += (unsigned long) p->addr -
				   (unsigned long) p->ainsn.insn;
	}

	disable_singlestep(kcb, regs, ip);
}
NOKPROBE_SYMBOL(resume_execution);

static int post_kprobe_handler(struct pt_regs *regs)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	struct kprobe *p = kprobe_running();

	if (!p)
		return 0;

	resume_execution(p, regs);
	if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
		kcb->kprobe_status = KPROBE_HIT_SSDONE;
		p->post_handler(p, regs, 0);
	}
	pop_kprobe(kcb);
	preempt_enable_no_resched();

	/*
	 * if somebody else is singlestepping across a probe point, psw mask
	 * will have PER set, in which case, continue the remaining processing
	 * of do_single_step, as if this is not a probe hit.
	 */
	if (regs->psw.mask & PSW_MASK_PER)
		return 0;

	return 1;
}
NOKPROBE_SYMBOL(post_kprobe_handler);

static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	struct kprobe *p = kprobe_running();

	switch(kcb->kprobe_status) {
	case KPROBE_HIT_SS:
	case KPROBE_REENTER:
		/*
		 * We are here because the instruction being single
		 * stepped caused a page fault. We reset the current
		 * kprobe and the nip points back to the probe address
		 * and allow the page fault handler to continue as a
		 * normal page fault.
		 */
		disable_singlestep(kcb, regs, (unsigned long) p->addr);
		pop_kprobe(kcb);
		preempt_enable_no_resched();
		break;
	case KPROBE_HIT_ACTIVE:
	case KPROBE_HIT_SSDONE:
		/*
		 * In case the user-specified fault handler returned
		 * zero, try to fix up.
		 */
		if (fixup_exception(regs))
			return 1;
		/*
		 * fixup_exception() could not handle it,
		 * Let do_page_fault() fix it.
		 */
		break;
	default:
		break;
	}
	return 0;
}
NOKPROBE_SYMBOL(kprobe_trap_handler);

int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
	int ret;

	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
		local_irq_disable();
	ret = kprobe_trap_handler(regs, trapnr);
	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
		local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
	return ret;
}
NOKPROBE_SYMBOL(kprobe_fault_handler);

/*
 * Wrapper routine to for handling exceptions.
 */
int kprobe_exceptions_notify(struct notifier_block *self,
			     unsigned long val, void *data)
{
	struct die_args *args = (struct die_args *) data;
	struct pt_regs *regs = args->regs;
	int ret = NOTIFY_DONE;

	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
		local_irq_disable();

	switch (val) {
	case DIE_BPT:
		if (kprobe_handler(regs))
			ret = NOTIFY_STOP;
		break;
	case DIE_SSTEP:
		if (post_kprobe_handler(regs))
			ret = NOTIFY_STOP;
		break;
	case DIE_TRAP:
		if (!preemptible() && kprobe_running() &&
		    kprobe_trap_handler(regs, args->trapnr))
			ret = NOTIFY_STOP;
		break;
	default:
		break;
	}

	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
		local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);

	return ret;
}
NOKPROBE_SYMBOL(kprobe_exceptions_notify);

int __init arch_init_kprobes(void)
{
	return 0;
}

int __init arch_populate_kprobe_blacklist(void)
{
	return kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
					 (unsigned long)__irqentry_text_end);
}

int arch_trampoline_kprobe(struct kprobe *p)
{
	return 0;
}
NOKPROBE_SYMBOL(arch_trampoline_kprobe);
Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0+
	2	/*
	3	* Kernel Probes (KProbes)
	4	*
	5	* Copyright IBM Corp. 2002, 2006
	6	*
	7	* s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
	8	*/
	9
	10	#define pr_fmt(fmt) "kprobes: " fmt
	11
	12	#include <linux/kprobes.h>
	13	#include <linux/ptrace.h>
	14	#include <linux/preempt.h>
	15	#include <linux/stop_machine.h>
	16	#include <linux/cpufeature.h>
	17	#include <linux/kdebug.h>
	18	#include <linux/uaccess.h>
	19	#include <linux/extable.h>
	20	#include <linux/module.h>
	21	#include <linux/slab.h>
	22	#include <linux/hardirq.h>
	23	#include <linux/ftrace.h>
	24	#include <linux/execmem.h>
	25	#include <asm/text-patching.h>
	26	#include <asm/set_memory.h>
	27	#include <asm/sections.h>
	28	#include <asm/dis.h>
	29	#include "entry.h"
	30
	31	DEFINE_PER_CPU(struct kprobe *, current_kprobe);
	32	DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
	33
	34	struct kretprobe_blackpoint kretprobe_blacklist[] = { };
	35
	36	void *alloc_insn_page(void)
	37	{
	38	void *page;
	39
	40	page = execmem_alloc(EXECMEM_KPROBES, PAGE_SIZE);
	41	if (!page)
	42	return NULL;
	43	set_memory_rox((unsigned long)page, 1);
	44	return page;
	45	}
	46
	47	static void copy_instruction(struct kprobe *p)
	48	{
	49	kprobe_opcode_t insn[MAX_INSN_SIZE];
	50	s64 disp, new_disp;
	51	u64 addr, new_addr;
	52	unsigned int len;
	53
	54	len = insn_length(*p->addr >> 8);
	55	memcpy(&insn, p->addr, len);
	56	p->opcode = insn[0];
	57	if (probe_is_insn_relative_long(&insn[0])) {
	58	/*
	59	* For pc-relative instructions in RIL-b or RIL-c format patch
	60	* the RI2 displacement field. The insn slot for the to be
	61	* patched instruction is within the same 4GB area like the
	62	* original instruction. Therefore the new displacement will
	63	* always fit.
	64	*/
	65	disp = (s32 )&insn[1];
	66	addr = (u64)(unsigned long)p->addr;
	67	new_addr = (u64)(unsigned long)p->ainsn.insn;
	68	new_disp = ((addr + (disp * 2)) - new_addr) / 2;
	69	(s32 )&insn[1] = new_disp;
	70	}
	71	s390_kernel_write(p->ainsn.insn, &insn, len);
	72	}
	73	NOKPROBE_SYMBOL(copy_instruction);
	74
	75	/* Check if paddr is at an instruction boundary */
	76	static bool can_probe(unsigned long paddr)
	77	{
	78	unsigned long addr, offset = 0;
	79	kprobe_opcode_t insn;
	80	struct kprobe *kp;
	81
	82	if (paddr & 0x01)
	83	return false;
	84
	85	if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
	86	return false;
	87
	88	/* Decode instructions */
	89	addr = paddr - offset;
	90	while (addr < paddr) {
	91	if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn)))
	92	return false;
	93
	94	if (insn >> 8 == 0) {
	95	if (insn != BREAKPOINT_INSTRUCTION) {
	96	/*
	97	* Note that QEMU inserts opcode 0x0000 to implement
	98	* software breakpoints for guests. Since the size of
	99	* the original instruction is unknown, stop following
	100	* instructions and prevent setting a kprobe.
	101	*/
	102	return false;
	103	}
	104	/*
	105	* Check if the instruction has been modified by another
	106	* kprobe, in which case the original instruction is
	107	* decoded.
	108	*/
	109	kp = get_kprobe((void *)addr);
	110	if (!kp) {
	111	/* not a kprobe */
	112	return false;
	113	}
	114	insn = kp->opcode;
	115	}
	116	addr += insn_length(insn >> 8);
	117	}
	118	return addr == paddr;
	119	}
	120
	121	int arch_prepare_kprobe(struct kprobe *p)
	122	{
	123	if (!can_probe((unsigned long)p->addr))
	124	return -EINVAL;
	125	/* Make sure the probe isn't going on a difficult instruction */
	126	if (probe_is_prohibited_opcode(p->addr))
	127	return -EINVAL;
	128	p->ainsn.insn = get_insn_slot();
	129	if (!p->ainsn.insn)
	130	return -ENOMEM;
	131	copy_instruction(p);
	132	return 0;
	133	}
	134	NOKPROBE_SYMBOL(arch_prepare_kprobe);
	135
	136	struct swap_insn_args {
	137	struct kprobe *p;
	138	unsigned int arm_kprobe : 1;
	139	};
	140
	141	static int swap_instruction(void *data)
	142	{
	143	struct swap_insn_args *args = data;
	144	struct kprobe *p = args->p;
	145	u16 opc;
	146
	147	opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
	148	s390_kernel_write(p->addr, &opc, sizeof(opc));
	149	return 0;
	150	}
	151	NOKPROBE_SYMBOL(swap_instruction);
	152
	153	void arch_arm_kprobe(struct kprobe *p)
	154	{
	155	struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
	156
	157	if (cpu_has_seq_insn()) {
	158	swap_instruction(&args);
	159	text_poke_sync();
	160	} else {
	161	stop_machine_cpuslocked(swap_instruction, &args, NULL);
	162	}
	163	}
	164	NOKPROBE_SYMBOL(arch_arm_kprobe);
	165
	166	void arch_disarm_kprobe(struct kprobe *p)
	167	{
	168	struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
	169
	170	if (cpu_has_seq_insn()) {
	171	swap_instruction(&args);
	172	text_poke_sync();
	173	} else {
	174	stop_machine_cpuslocked(swap_instruction, &args, NULL);
	175	}
	176	}
	177	NOKPROBE_SYMBOL(arch_disarm_kprobe);
	178
	179	void arch_remove_kprobe(struct kprobe *p)
	180	{
	181	if (!p->ainsn.insn)
	182	return;
	183	free_insn_slot(p->ainsn.insn, 0);
	184	p->ainsn.insn = NULL;
	185	}
	186	NOKPROBE_SYMBOL(arch_remove_kprobe);
	187
	188	static void enable_singlestep(struct kprobe_ctlblk *kcb,
	189	struct pt_regs *regs,
	190	unsigned long ip)
	191	{
	192	union {
	193	struct ctlreg regs[3];
	194	struct {
	195	struct ctlreg control;
	196	struct ctlreg start;
	197	struct ctlreg end;
	198	};
	199	} per_kprobe;
	200
	201	/* Set up the PER control registers %cr9-%cr11 */
	202	per_kprobe.control.val = PER_EVENT_IFETCH;
	203	per_kprobe.start.val = ip;
	204	per_kprobe.end.val = ip;
	205
	206	/* Save control regs and psw mask */
	207	__local_ctl_store(9, 11, kcb->kprobe_saved_ctl);
	208	kcb->kprobe_saved_imask = regs->psw.mask &
	209	(PSW_MASK_PER \| PSW_MASK_IO \| PSW_MASK_EXT);
	210
	211	/* Set PER control regs, turns on single step for the given address */
	212	__local_ctl_load(9, 11, per_kprobe.regs);
	213	regs->psw.mask \|= PSW_MASK_PER;
	214	regs->psw.mask &= ~(PSW_MASK_IO \| PSW_MASK_EXT);
	215	regs->psw.addr = ip;
	216	}
	217	NOKPROBE_SYMBOL(enable_singlestep);
	218
	219	static void disable_singlestep(struct kprobe_ctlblk *kcb,
	220	struct pt_regs *regs,
	221	unsigned long ip)
	222	{
	223	/* Restore control regs and psw mask, set new psw address */
	224	__local_ctl_load(9, 11, kcb->kprobe_saved_ctl);
	225	regs->psw.mask &= ~PSW_MASK_PER;
	226	regs->psw.mask \|= kcb->kprobe_saved_imask;
	227	regs->psw.addr = ip;
	228	}
	229	NOKPROBE_SYMBOL(disable_singlestep);
	230
	231	/*
	232	* Activate a kprobe by storing its pointer to current_kprobe. The
	233	* previous kprobe is stored in kcb->prev_kprobe. A stack of up to
	234	* two kprobes can be active, see KPROBE_REENTER.
	235	*/
	236	static void push_kprobe(struct kprobe_ctlblk kcb, struct kprobe p)
	237	{
	238	kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
	239	kcb->prev_kprobe.status = kcb->kprobe_status;
	240	__this_cpu_write(current_kprobe, p);
	241	}
	242	NOKPROBE_SYMBOL(push_kprobe);
	243
	244	/*
	245	* Deactivate a kprobe by backing up to the previous state. If the
	246	* current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
	247	* for any other state prev_kprobe.kp will be NULL.
	248	*/
	249	static void pop_kprobe(struct kprobe_ctlblk *kcb)
	250	{
	251	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
	252	kcb->kprobe_status = kcb->prev_kprobe.status;
	253	kcb->prev_kprobe.kp = NULL;
	254	}
	255	NOKPROBE_SYMBOL(pop_kprobe);
	256
	257	static void kprobe_reenter_check(struct kprobe_ctlblk kcb, struct kprobe p)
	258	{
	259	switch (kcb->kprobe_status) {
	260	case KPROBE_HIT_SSDONE:
	261	case KPROBE_HIT_ACTIVE:
	262	kprobes_inc_nmissed_count(p);
	263	break;
	264	case KPROBE_HIT_SS:
	265	case KPROBE_REENTER:
	266	default:
	267	/*
	268	* A kprobe on the code path to single step an instruction
	269	* is a BUG. The code path resides in the .kprobes.text
	270	* section and is executed with interrupts disabled.
	271	*/
	272	pr_err("Failed to recover from reentered kprobes.\n");
	273	dump_kprobe(p);
	274	BUG();
	275	}
	276	}
	277	NOKPROBE_SYMBOL(kprobe_reenter_check);
	278
	279	static int kprobe_handler(struct pt_regs *regs)
	280	{
	281	struct kprobe_ctlblk *kcb;
	282	struct kprobe *p;
	283
	284	/*
	285	* We want to disable preemption for the entire duration of kprobe
	286	* processing. That includes the calls to the pre/post handlers
	287	* and single stepping the kprobe instruction.
	288	*/
	289	preempt_disable();
	290	kcb = get_kprobe_ctlblk();
	291	p = get_kprobe((void *)(regs->psw.addr - 2));
	292
	293	if (p) {
	294	if (kprobe_running()) {
	295	/*
	296	* We have hit a kprobe while another is still
	297	* active. This can happen in the pre and post
	298	* handler. Single step the instruction of the
	299	* new probe but do not call any handler function
	300	* of this secondary kprobe.
	301	* push_kprobe and pop_kprobe saves and restores
	302	* the currently active kprobe.
	303	*/
	304	kprobe_reenter_check(kcb, p);
	305	push_kprobe(kcb, p);
	306	kcb->kprobe_status = KPROBE_REENTER;
	307	} else {
	308	/*
	309	* If we have no pre-handler or it returned 0, we
	310	* continue with single stepping. If we have a
	311	* pre-handler and it returned non-zero, it prepped
	312	* for changing execution path, so get out doing
	313	* nothing more here.
	314	*/
	315	push_kprobe(kcb, p);
	316	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
	317	if (p->pre_handler && p->pre_handler(p, regs)) {
	318	pop_kprobe(kcb);
	319	preempt_enable_no_resched();
	320	return 1;
	321	}
	322	kcb->kprobe_status = KPROBE_HIT_SS;
	323	}
	324	enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
	325	return 1;
	326	} /* else:
	327	* No kprobe at this address and no active kprobe. The trap has
	328	* not been caused by a kprobe breakpoint. The race of breakpoint
	329	* vs. kprobe remove does not exist because on s390 as we use
	330	* stop_machine to arm/disarm the breakpoints.
	331	*/
	332	preempt_enable_no_resched();
	333	return 0;
	334	}
	335	NOKPROBE_SYMBOL(kprobe_handler);
	336
	337	/*
	338	* Called after single-stepping. p->addr is the address of the
	339	* instruction whose first byte has been replaced by the "breakpoint"
	340	* instruction. To avoid the SMP problems that can occur when we
	341	* temporarily put back the original opcode to single-step, we
	342	* single-stepped a copy of the instruction. The address of this
	343	* copy is p->ainsn.insn.
	344	*/
	345	static void resume_execution(struct kprobe p, struct pt_regs regs)
	346	{
	347	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	348	unsigned long ip = regs->psw.addr;
	349	int fixup = probe_get_fixup_type(p->ainsn.insn);
	350
	351	if (fixup & FIXUP_PSW_NORMAL)
	352	ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
	353
	354	if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
	355	int ilen = insn_length(p->ainsn.insn[0] >> 8);
	356	if (ip - (unsigned long) p->ainsn.insn == ilen)
	357	ip = (unsigned long) p->addr + ilen;
	358	}
	359
	360	if (fixup & FIXUP_RETURN_REGISTER) {
	361	int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
	362	regs->gprs[reg] += (unsigned long) p->addr -
	363	(unsigned long) p->ainsn.insn;
	364	}
	365
	366	disable_singlestep(kcb, regs, ip);
	367	}
	368	NOKPROBE_SYMBOL(resume_execution);
	369
	370	static int post_kprobe_handler(struct pt_regs *regs)
	371	{
	372	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	373	struct kprobe *p = kprobe_running();
	374
	375	if (!p)
	376	return 0;
	377
	378	resume_execution(p, regs);
	379	if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
	380	kcb->kprobe_status = KPROBE_HIT_SSDONE;
	381	p->post_handler(p, regs, 0);
	382	}
	383	pop_kprobe(kcb);
	384	preempt_enable_no_resched();
	385
	386	/*
	387	* if somebody else is singlestepping across a probe point, psw mask
	388	* will have PER set, in which case, continue the remaining processing
	389	* of do_single_step, as if this is not a probe hit.
	390	*/
	391	if (regs->psw.mask & PSW_MASK_PER)
	392	return 0;
	393
	394	return 1;
	395	}
	396	NOKPROBE_SYMBOL(post_kprobe_handler);
	397
	398	static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
	399	{
	400	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	401	struct kprobe *p = kprobe_running();
	402
	403	switch(kcb->kprobe_status) {
	404	case KPROBE_HIT_SS:
	405	case KPROBE_REENTER:
	406	/*
	407	* We are here because the instruction being single
	408	* stepped caused a page fault. We reset the current
	409	* kprobe and the nip points back to the probe address
	410	* and allow the page fault handler to continue as a
	411	* normal page fault.
	412	*/
	413	disable_singlestep(kcb, regs, (unsigned long) p->addr);
	414	pop_kprobe(kcb);
	415	preempt_enable_no_resched();
	416	break;
	417	case KPROBE_HIT_ACTIVE:
	418	case KPROBE_HIT_SSDONE:
	419	/*
	420	* In case the user-specified fault handler returned
	421	* zero, try to fix up.
	422	*/
	423	if (fixup_exception(regs))
	424	return 1;
	425	/*
	426	* fixup_exception() could not handle it,
	427	* Let do_page_fault() fix it.
	428	*/
	429	break;
	430	default:
	431	break;
	432	}
	433	return 0;
	434	}
	435	NOKPROBE_SYMBOL(kprobe_trap_handler);
	436
	437	int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
	438	{
	439	int ret;
	440
	441	if (regs->psw.mask & (PSW_MASK_IO \| PSW_MASK_EXT))
	442	local_irq_disable();
	443	ret = kprobe_trap_handler(regs, trapnr);
	444	if (regs->psw.mask & (PSW_MASK_IO \| PSW_MASK_EXT))
	445	local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
	446	return ret;
	447	}
	448	NOKPROBE_SYMBOL(kprobe_fault_handler);
	449
	450	/*
	451	* Wrapper routine to for handling exceptions.
	452	*/
	453	int kprobe_exceptions_notify(struct notifier_block *self,
	454	unsigned long val, void *data)
	455	{
	456	struct die_args args = (struct die_args ) data;
	457	struct pt_regs *regs = args->regs;
	458	int ret = NOTIFY_DONE;
	459
	460	if (regs->psw.mask & (PSW_MASK_IO \| PSW_MASK_EXT))
	461	local_irq_disable();
	462
	463	switch (val) {
	464	case DIE_BPT:
	465	if (kprobe_handler(regs))
	466	ret = NOTIFY_STOP;
	467	break;
	468	case DIE_SSTEP:
	469	if (post_kprobe_handler(regs))
	470	ret = NOTIFY_STOP;
	471	break;
	472	case DIE_TRAP:
	473	if (!preemptible() && kprobe_running() &&
	474	kprobe_trap_handler(regs, args->trapnr))
	475	ret = NOTIFY_STOP;
	476	break;
	477	default:
	478	break;
	479	}
	480
	481	if (regs->psw.mask & (PSW_MASK_IO \| PSW_MASK_EXT))
	482	local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
	483
	484	return ret;
	485	}
	486	NOKPROBE_SYMBOL(kprobe_exceptions_notify);
	487
	488	int __init arch_init_kprobes(void)
	489	{
	490	return 0;
	491	}
	492
	493	int __init arch_populate_kprobe_blacklist(void)
	494	{
	495	return kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
	496	(unsigned long)__irqentry_text_end);
	497	}
	498
	499	int arch_trampoline_kprobe(struct kprobe *p)
	500	{
	501	return 0;
	502	}
	503	NOKPROBE_SYMBOL(arch_trampoline_kprobe);